Prevalence of signs of lower urinary tract disease and positive urine culture in dogs with diabetes mellitus: A retrospective study

Abstract Background No recent studies have evaluated the association between clinical signs of lower urinary tract disease (LUTD) and positive urine culture in dogs with diabetes mellitus. Objective Determine the prevalence of subclinical bacteriuria (ie, positive urine culture without signs of LUTD) in dogs with diabetes mellitus. Animals One hundred seven dogs with diabetes mellitus were evaluated at a university veterinary hospital. Methods Retrospective study evaluating diabetic dogs with a single sample paired urinalysis and urine culture. Relationship between the presence of signs of LUTD, pyuria, and bacteriuria and urine culture results were compared using Fisher exact testing. Results Fifteen dogs (14%) had a positive urine culture via cystocentesis or free catch, of which 8 (53%) had pyuria, and 4 (27%) had signs of LUTD. Of the 88 dogs (82%) without signs of LUTD, 11 (13%) had a positive culture. A significant association was found between a positive urine culture and pyuria (OR infinity; 95% CI 20.34‐infinity, P < .00001) and bacteriuria (OR infinity; 95% CI 164.4‐infinity, P < .00001). No association was found between urine culture results and signs of LUTD (OR 1.87; 95% CI 0.59‐6.85, P = .46). Conclusion and Clinical Importance Subclinical bacteriuria occurred in this cohort of dogs, and our findings reinforce the recommendation that urine cultures should not be routinely performed in diabetic dogs particularly if pyuria and bacteriuria are absent.


| INTRODUCTION
Recommendations for when to submit urine cultures in diabetic dogs have dramatically changed over the last 25 years. Previously, routine submission of urine cultures was recommended and commonly performed in diabetic dogs regardless of clinical signs or urinalysis results. 1,2 Reasons for this recommendation included concerns for infection promoting insulin resistance and diabetic ketoacidosis, increased risk for urinary tract infections because of altered immune function of immune cells such as granulocytes, and these potential lower urinary tract infections serving as a source of septicemia if left untreated. [1][2][3] In human medicine, a urinary tract infection (UTI) in a diabetic patient was categorized as a complicated UTI and this verbiage was initially adopted in veterinary medicine. 4 Studies in dogs show that a positive urine culture can occur without signs of lower urinary tract disease (LUTD) or expected urine sediment changes such as pyuria or cytologic presence of bacteria. 1,2,5 Therefore, screening urinalyses and urine cultures in diabetic dogs were commonly performed in general and specialty practice.
Over time these recommendations have changed to mirror current human guidelines and to support better antimicrobial stewardship in veterinary medicine. Consensus guidelines for antimicrobial use in animals discouraged the submission of urine cultures in dogs that are not showing signs of lower urinary tract disease. 6 Expected signs of LUTD associated with a UTI could include stranguria, pollakiuria, dysuria, malodorous urine, hematuria, inappropriate urination, or a combination of these signs. 7,8 The consensus guidelines also recommended to not treat subclinical bacteriuria (SB). Subclinical bacteriuria is defined as a positive bacterial urine culture in an animal that is not showing any clinical signs of urinary tract disease. 8 In humans, asymptomatic bacteriuria (AB) is a common finding, particularly in healthy women or individuals with concurrent urologic abnormalities. 9 Screening for AB is only recommended in certain clinical scenarios such as in pregnant women or in patients undergoing invasive endourologic procedures. Screening or treating for AB is not recommended in people with diabetes mellitus. 9 Subclinical bacteriuria under the current definition also occurs in healthy dogs 5,10,11 and is documented in diabetic dogs. 1 antimicrobial was prescribed. Additionally, any available follow-up information after the initial visit was recorded. If the route of urine collection was not listed within the medical record and could not be determined, the sample was assigned to the voided group. The definitions used to describe WBC and RBC numbers are the following: rare and trace were considered equivalent terminology, rare was defined as 1 to 10 cells on the entire slide for both WBCs and RBCs, occasional was defined as 0 to 5 cells per hpf for RBCs and 0 to 3 cells per hpf for WBCs, and packed field was defined as many cells were present where the determination of an actual number was not possible. During the study timeframe, the laboratory changed how casts were reported. For the purposes of the study, both classifications (descriptive and numerical) were recorded. For the descriptive classifications, the terms were defined as the following: few casts were defined as 0% to 10% per hpf, difficult to find on the slide, and up to one or more in almost every field; moderate casts were defined as 10% to 50% per hpf, easy to find, and the number present in the field of view (FOV) varies; and many casts were defined as >50% per hpf with a large number present on all FOVs. For the numerical classifications, 0 to 1, 1 to 3, 3 to 6, 6 to 10, and >10 casts present per low power field (lpf) were recorded.
Routine urinalysis with sediment examination was performed by the clinical pathology service with at least 5 mL of freshly submitted refrigerated urine within a few hours as described. 12 At least a 1 mL aliquot of urine was submitted for urine culture to the Colorado State University Veterinary Diagnostic Laboratory.

| Animals
This study initially contained 657 potential paired urinalysis and culture samples for evaluation but after screening for exclusion criteria, 107 dogs were included for evaluation. Median age was 9 years old (range 14 weeks-15 years

| Urinalysis
The route of urine collection was predominantly via cystocentesis (96/107, 89.7%) and the remaining samples were collected from voided urine. All samples were refrigerated and processed by the diagnostic laboratory within a few hours, and all were cultured on-site as per our standard protocol. Urine specific gravity (USG) ranged from 1.006 to 1.073, with a median value of 1.033. The urine pH minimum was 5.0 and the maximum was 9.0, with a median value 6.4.
Crystalluria was rare and included amorphous 5.6% ( Cytologic presence of bacteria was noted in 15% of samples (16/107). When the number of bacteria was quantified into groups, 2 samples were recorded as "few," 6 samples were recorded as "moderate," and 7 were recorded as "many." In one sample, the num-  Pseudomonas aeruginosa (7%, 1/15). One culture grew Aspergillus spp., which was considered contaminated by the clinical pathology lab and not a true positive. As such, this urine sample was reported in the "No Growth" category. Of the samples that cultured E. coli, 5 samples isolated E. coli hemolytic and one isolated an equal mixture of both colonies (ie, E. coli and E. coli hemolytic). In the samples that cultured bacteria, the majority had >100 000 cfu/mL (46.7%, 7/15). Of those 7 urine cultures, 6 grew a single isolate at 100000 cfu/mL.

| Changes in insulin treatment
Out of the 11 dogs that had subclinical bacteriuria, 3/11 (27%) had a change in insulin dosage. The insulin dose was decreased in these 3 dogs because of concern for overregulation of diabetes mellitus because of the findings of suspected seizure-like activity and intermittent concurrent hypoglycemia events, episodes of collapse shortly after receiving insulin, and intermittent periods of lack of glucose in the urine. The remaining 8 dogs with subclinical bacteriuria (8/11, 73%) had no change in insulin treatment.  ing SB in animals thought to be at risk for ascending infection such as patients with chronic kidney disease or that are immunocompromised 7 however, the recent guidelines 8 suggest that there is a lack of evidence to support treatment of SB in any animal, regardless of comorbidities. This is based on the lack of evidence found in human literature to support treatment of AB in either healthy individuals or those with comorbidities including endocrinopathies 9 however more prospective studies with outcome measures are also needed in human medicine. Treatment of bacteriuria in humans without clinical signs increases the risk of adverse drug reactions and promotes antimicrobial resistance and often will result in recolonization of bacteria and lack of appropriate bacterial clearance. 9 This recommendation is for both healthy, and diabetic patients, 9 and there is no current strong evidence to suggest that dogs should be treated differently from human patients in this regard.

| Follow-up information
There are limitations to our study. An inherent limitation is because of the retrospective nature of the study design and lack of standardized follow-up and diagnostics. However, the medical records utilized for this study were obtained from an academic hospital with extensive patient histories. To ensure signs of LUTD were not confused with signs of urinary incontinence at the initial evaluation, any dog with a diagnosis of urinary incontinence, USMI, or was currently on medications for control (diethylstilbestrol, phenylpropanolamine, etc.) of urinary incontinence was excluded. Although polyuria could be considered a sign of LUTD, it was not included in our definition for diabetic dogs as polyuria could be a common manifestation of a poorly regulated diabetic. Another limitation already mentioned is that the presence of signs of LUTD was based on retrospective evaluation of medical records and reliance on the owner to report such observations. Signs of LUTD may have been present but not communicated to the veterinarian writing the medical record. Less likely, signs of LUTD could have been mentioned by the client but not recorded within the medical record or misinterpreted as uncontrolled diabetes mellitus or urinary incontinence. Another limitation of this study because of the retrospective study design is that we cannot make

CONFLICT OF INTEREST DECLARATION
Authors declare no conflict of interest.

OFF-LABEL ANTIMICROBIAL DECLARATION
Authors declare no off-label use of antimicrobials.

INSTITUTIONAL ANIMAL CARE AND USE COMMITTEE (IACUC) OR OTHER APPROVAL DECLARATION
Authors declare no IACUC or other approval was needed.

HUMAN ETHICS APPROVAL DECLARATION
Authors declare human ethics approval was not needed for this study.